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This outbreak appears to be over. However, Listeria remains an important cause of serious, life-threatening human illness in the United States. For more information about Listeria and steps that people can take to reduce their risk of infection, visit CDC’s Listeria webpage.

Highlights

This outbreak appears to be over. However, Listeria remains an important cause of serious, life-threatening human illness in the United States. For more information about Listeria and steps that people can take to reduce their risk of infection, visit CDC’s Listeria webpage.

CDC, several states, and the U.S. Food and Drug Administration (FDA) investigated a multistate outbreak of Listeria monocytogenes infections (listeriosis).

A total of 19 people infected with the outbreak strain of Listeria were reported from nine states.

All 19 people were hospitalized, and one person from Michigan died as a result of listeriosis. One illness was reported in a pregnant woman.

Whole genome sequencing (WGS) performed on Listeria isolates from all 19 ill people showed that the isolates were closely related genetically.

WGS performed on clinical isolates from ill people in Canada showed that the isolates were closely related genetically to Listeria isolates from ill people in the United States.

Epidemiologic and laboratory evidence indicated that packaged salads produced at the Dole processing facility in Springfield, Ohio and sold under various brand names were the likely source of this outbreak.

On January 27, 2016, Dole voluntarily recalled all salad mixes produced in the Springfield, Ohio processing facility. Any recalled salad mixes still on the market or in consumers’ homes would be past their expiration dates.

Outbreak Summary

Introduction

CDC collaborated with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeriamonocytogenes infections (listeriosis). Listeria can cause a serious, life-threatening illness.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA “fingerprinting” is performed on Listeria bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE.

A total of 19 people infected with the outbreak strain of Listeria were reported from nine states. A list of states and the number of cases in each can be found on the Case Count Map page.

Listeria specimens were collected from July 5, 2015 to January 31, 2016. Ill people ranged in age from 3 years to 83, and the median age was 64. Of ill people, 74% were female. All 19 (100%) ill people were reported as hospitalized, and 1 person from Michigan died as a result of listeriosis. One of the illnesses reported was in a pregnant woman. WGS was performed on Listeria isolates from all 19 ill people and showed that the isolates were closely related genetically. This close genetic relationship means that people in this outbreak were more likely to share a common source of infection, such as a contaminated food.

According to the Public Health Agency of Canada, ill people in Canada were infected with the same outbreak strain of Listeria. Whole genome sequencing of clinical isolates from ill people in Canada showed that the isolates were closely related genetically to Listeria isolates from ill people in the United States.

Investigation of the Outbreak

Epidemiologic and laboratory evidence indicated that packaged salads produced at the Dole processing facility in Springfield, Ohio and sold under various brand names were the likely source of this outbreak.

State and local health departments interviewed ill people about the foods they may have eaten or other exposures in the month before their illness began. Of 14 ill people who were asked about packaged salad, 13 (93%) reported eating a packaged salad. All of the 9 ill people who specified the brand of packaged salad eaten reported various kinds of Dole brand packaged salad.

As part of a routine product sampling program, the Ohio Department of Agriculture collected a Dole brand Field Greens packaged salad from a retail location and isolated Listeria. This packaged salad was produced at the Springfield, Ohio Dole processing facility. In January 2016, WGS showed that the Listeria isolate from the packaged salad was closely related genetically to isolates from ill people. This information helped link the illnesses to Dole brand packaged salads produced at the Dole processing facility in Springfield, Ohio. Additionally, the Public Health Agency of Canada confirmed the presence of Listeria in packaged salads produced at the Dole Springfield, Ohio processing facility.

On January 21, 2016, Dole reported to CDC that it had stopped production at the processing facility in Springfield, Ohio and withdrew packaged salads from this facility that were on the market at that time. On January 27, 2016, Dole voluntarily recalled all salad mixes produced in the Springfield, Ohio processing facility. The recall included several brands and varieties of salad mixes that were distributed throughout the United States and in Eastern Canada. The type of salad mixes produced at this facility were packaged in bags and plastic clamshell containers and were identified by the letter “A” at the beginning of the manufacturing code on the package. Any recalled salad mixes still on the market or in consumers’ homes would be past their expiration dates.

February 25, 2016

Case Count Update

Since the last update on January 28, three more ill people have been reported from Missouri (1) and Ohio (2).

Eighteen people infected with the outbreak strain of Listeria have been reported from nine states since July 5, 2015. The number of ill people reported from each state is as follows: Connecticut (1), Indiana (1), Massachusetts (1), Michigan (4), Missouri (2), New Jersey (1), New York (5), Ohio (2), and Pennsylvania (1). Whole genome sequencing has been performed on clinical isolates from all ill people and has shown that the isolates are highly related genetically.

Listeria specimens were collected from ill people between July 5, 2015 and January 31, 2016. Ill people range in age from 3 years to 83, and the median age is 66. Seventy-two percent of ill people are female. All 18 (100%) ill people were hospitalized, including one person from Michigan who died as a result of listeriosis. One of the illnesses reported was in a pregnant woman.

January 28, 2016

Case Count Update

Since the last update on January 22, three more ill people have been reported from Connecticut, Missouri, and New York.

Fifteen people infected with the outbreak strain of Listeria have been reported from eight states since July 5, 2015. The number of ill people reported from each state is as follows: Connecticut (1), Indiana (1), Massachusetts (1), Michigan (4), Missouri (1), New Jersey (1), New York (5), and Pennsylvania (1). Whole genome sequencing has been performed on clinical isolates from all ill people and has shown that the isolates are highly related genetically.

Listeria specimens were collected from ill people between July 5, 2015 and January 3, 2016. Ill people range in age from 3 years to 83, and the median age is 64. Seventy-three percent of ill people are female. All 15 (100%) ill people were hospitalized, including one person from Michigan who died as a result of listeriosis. One of the illnesses reported was in a pregnant woman.

Investigation Update

State and local health departments and federal investigators continue to interview ill people about the foods they may have eaten or other exposures in the month before their illness began. Of eight ill people who were asked about packaged salad, all eight (100%) reported eating a packaged salad. Four (100%) of four ill people who were able to specify the brands of packaged salad they ate reported various kinds of Dole brand packaged salad.

On January 27, 2016, Dole voluntarily recalled all salad mixes produced in the Springfield, Ohio processing facility. At this time, there is no evidence to suggest that any products produced at other Dole processing facilities in the United States are linked to illness. The type of salad mixes produced at this facility were packaged in bags and plastic clamshell containers and can be identified by the letter “A” at the beginning of the manufacturing code on the package.

According to the Public Health Agency of Canada, there are seven people in five Canadian provinces infected with the same outbreak strain of Listeria. Laboratory tests performed to date on clinical isolates from ill people in Canada showed that the isolates are highly related genetically to Listeria isolates from ill people in the United States. Packaged salads produced at the Springfield, Ohio Dole processing facility were distributed in Eastern Canada and the United States. Additionally, the Public Health Agency of Canada confirmed the presence of Listeria in packaged salads produced at the Dole Springfield, Ohio processing facility.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them. Updates will be provided when more information is available.

January 22, 2016

Initial Announcement

Since September 2015, CDC has been collaborating with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeriamonocytogenes infections (listeriosis). Listeria can cause a serious, life-threatening illness.

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA “fingerprinting” is performed on Listeria bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE.

Twelve people infected with the outbreak strain of Listeria have been reported from six states since July 5, 2015. The number of ill people reported from each state is as follows: Indiana (1), Massachusetts (1), Michigan (4), New Jersey (1), New York (4), and Pennsylvania (1). WGS has been performed on clinical isolates from all 12 ill people and has shown that the isolates are highly related genetically.

Listeria specimens were collected from July 5, 2015 to December 23, 2015. Ill people range in age from 3 years to 83, and the median age is 66. Sixty-nine percent of ill people are female. All 12 (100%) ill people reported being hospitalized, including one person from Michigan who died as a result of listeriosis. One of the illnesses reported was in a pregnant woman.

The outbreak can be illustrated with a chart showing the number of people who were diagnosed each week. This chart is called an epidemic curve or epi curve.

Investigation of the Outbreak

Epidemiologic and laboratory evidence available at this time indicates that packaged salads produced at the Dole processing facility in Springfield, Ohio and sold under various brand names are the likely source of this outbreak.

State and local health departments are interviewing ill people about the foods they may have eaten or other exposures in the month before their illness began. Of five ill people who were asked about packaged salad, all five (100%) reported eating a packaged salad. Two (100%) of two ill people who specified the brand of packaged salad eaten reported various varieties of Dole brand packaged salad.

As part of a routine product sampling program, the Ohio Department of Agriculture collected a Dole brand Field Greens packaged salad from a retail location and isolated Listeria. This packaged salad was produced at the Springfield, Ohio Dole processing facility. In January 2016, WGS showed that the Listeria isolate from the packaged salad was highly related genetically to isolates from ill people. This information linked the illnesses to Dole brand packaged salads produced at the Dole processing facility in Springfield, Ohio.

On January 21, 2016, Dole reported to CDC that it had stopped production at the processing facility in Springfield, Ohio. The company also reported that it is withdrawing packaged salads currently on the market that were produced at this facility. The withdrawal does not affect other Dole products.

CDC recommends that consumers do not eat, restaurants do not serve, and retailers do not sell packaged salads produced at the Dole processing facility in Springfield, Ohio. These packaged salads were sold under various brand names, including Dole, Fresh Selections, Simple Truth, Marketside, The Little Salad Bar, and President’s Choice Organics. The packaged salads can be identified by the letter “A” at the beginning of the manufacturing code found on the package. At this time, there is no evidence to suggest that packaged salads produced at other Dole processing facilities in the United States are linked to illness.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them. Updates will be provided when more information is available.